The main parameter that will determine the price of your ticket is the time of the year you wil take your first flight : because many airfares are based on when you start your trip. The lowest fares occur in low season and the highest fares are in high season !

Travelers' Seasons

Here is a chart of the travalers' seasons (which can change some time to time, and depending on the airlines):

Considering that the price of the ticket is partly based on the Touristic season : if the price is an issue you will have to be flexible with the dates.

Then will raise the question : Price or Season ?